Transfer Freestyle Line Set & Style?
It is possible to import (append/link) a Line Style from another file.

Appending or linking line style is the same as with all other datablocks.


Press Shift+F1 to append. Press Ctrl+Alt+O to link.
In the file browser, which opens up, navigate to the blend file, which contains the line style. Clicking on the blend file will open up the file datablock structure, the types are sorted into folders. Open the FreestyleLineStyle folder and choose your desired style datablocks. 
The appended/linked line styles can now be chosen from the dropdown menu.